Design, fabrication, and optical gain performance of the gain-guided and index-antiguided Nd 3+ -doped phosphate glass fiber

Design, fabrication, and optical gain performance of the gain-guided and index-antiguided (GG-IAG) fiber are studied systematically in this work. The main parameters of the GG-IAG fiber, i.e., a, Δn, g, and η, are designed by single-mode operation theories, followed by a detailed study of the fabrication of the GG-IAG fiber, including preform design and fabrication, fiber-drawing conditions, and so on. GG-IAG fibers with different core diameters (100–380 μm) are obtained and their corresponding performance is measured. In order to verify whether the parameters of the fabricated GG-IAG fiber meet the theoretical design, the laser amplifier experiments of the GG-IAG fiber and the fabricated gain-guided and index-guided (GG-IG) fiber are both demonstrated. The experimental results show that the net optical gain coefficient of the GG-IG fiber is the sum of the net optical gain coefficient and the leakage loss coefficient of the GG-IAG fiber, which indicates that the fabricated GG-IAG fiber parameters and performance are consistent with the theoretical design. This work should help further exploration of the GG-IAG fiber.